Oncolytic Virus Therapy Shows Promising Results in Early-Stage TNBC

When added to systemic chemotherapy, the oncolytic virus talimogene laherparepvec (T-VEC) may improve responses in patients with high-risk, early-stage triple-negative breast cancer (TNBC), results of a phase 2 trial published in Nature Medicine suggest.¹

TNBC has historically been linked to worse overall outcomes and disproportionately high mortality relative to hormone-receptor–positive and HER2-positive breast cancers due to its lack of therapeutic targets, the authors noted. Although the treatment landscape for TNBC has shifted in recent years to include pembrolizumab and chemotherapy, systemic immunotherapy increases the risk of autoimmune adverse events, they added.

Oncolytic viruses injected intratumorally present a localized immunotherapy option. T-VEC, a modified oncolytic herpes simplex 1 virus, was approved by the FDA for the treatment of unresectable recurrent melanoma in 2015, and a recent phase 1 trial found that T-VEC plus neoadjuvant chemotherapy to be a safe and feasible approach to treating TNBC tumors.^2,3

The phase 2 trial of T-VEC plus neoadjuvant chemotherapy (NCT02779855) included 37 patients with stage 2 or 3 TNBC. Patients received 5 intratumoral injections of T-VEC in combination with paclitaxel, followed by doxorubicin and cyclophosphamide, then surgery to determine each patient’s residual cancer burden index (RCB). The main end point was the rate of RCB0, and secondary end points included RCB0-1 rates, the rate of recurrence, toxicity, and insight into potential immune biomarkers.

“Investigation of new agents in the neoadjuvant setting is an ideal way to interrogate their activity,” the authors wrote. “This may be particularly important for immunotherapy agents to allow the patient’s immune system to activate against tumor-associated antigens before tumor excision and the onset of chemotherapy-induced immunosuppression.”

Sixteen RCB0 pathological complete responses (pCRs) occurred, with an estimated pCR rate of 45.9%. Additionally, 8 patients showed RCB1 minimal residual disease, with a descriptive RCB0-1 rate of 65%. At 2 years post treatment, 89% of patients were still disease free, and the RCB0-1 patients did not experience any recurrences. In the overall group, there were 4 distant disease recurrences, 1 of which resulted in death.

The toxicity profile of T-VEC plus neoadjuvant chemotherapy was not significantly different from chemotherapy alone, although there were increases in brief low-grade fevers, chills, headaches, and pain at injection sites associated with T-VEC.

In the biomarker analysis, researchers found an increased immune signaling pathway activation in most tumors during the initial 6 weeks of treatment, followed by decreased but still higher than baseline activation once neoadjuvant chemotherapy was completed. Higher levels of CD8 T cells at week 6 were also associated with better responses to therapy. Further research in this area is warranted, the authors concluded.

Overall, the results suggest there is potential in T-VEC plus neoadjuvant chemotherapy as a treatment strategy for patients with TNBC.

“Our results demonstrate that TVEC, when added to systemic chemotherapy, may increase responses in high-risk, early-stage TNBC,” lead study author Hatem Soliman, MD, medical director of Moffitt Cancer Center’s clinical trials office and senior member of the Breast Oncology Department at Moffitt, said in a statement.⁴ “There is evidence of robust immune activation within the tumor, and additional investigation of T-VEC in combination with current chemoimmunotherapy for triple-negative breast cancer is warranted.”

References

1. Soliman H, Hogue D, Han H, et al. Oncolytic T-VEC virotherapy plus neoadjuvant chemotherapy in nonmetastatic triple-negative breast cancer: a phase 2 trial. Nat Med. 2023;29(2):450-457. doi:10.1038/s41591-023-02210-0

2. FDA approves IMLYGIC (talimogene laherparepvec) as first oncolytic viral therapy in the US. News release. Amgen. October 27, 2015. Accessed February 22, 2023. https://www.amgen.com/newsroom/press-releases/2015/10/fda-approves-imlygic-talimogene-laherparepvec-as-first-oncolytic-viral-therapy-in-the-us

3. Soliman, H. et al. A phase I trial of talimogene laherparepvec in combination with neoadjuvant chemotherapy for the treatment of nonmetastatic triple-negative breast cancer. Clin Cancer Res. 2021;27(4):1012-1018. doi:10.1158/1078-0432.CCR-20-3105

4. Oncolytic virus treatment produces promising results in patients with triple-negative breast cancer. News release. Moffitt Cancer Center. February 9, 2023. Accessed February 22, 2023. https://moffitt.org/newsroom/press-release-archive/oncolytic-virus-treatment-produces-promising-results-in-patients-with-triple-negative-breast-cancer/